Aldehyde-based resins such as urea formaldehyde (UF), melamine formaldehyde (MF), melamine-urea formaldehyde (MUF), and phenol formaldehyde (PF) resins are used as adhesives in the wood-based panel (WBP) production industries. However, using aldehyde-based resins as adhesives may be associated with some disadvantages such as formaldehyde emission during and after production of WBPs. Two factors may contribute to the formaldehyde emission from WBPs, free formaldehyde which exists in the adhesive, and hydrolysis of the cured aldehyde-based resins. Formaldehyde is reported to be a probable human carcinogen by different agencies such as international agency for research on cancer (2006), European chemicals agency for risk assessment (2010) and environmental protection agency (2012). As a result, there is an ongoing struggle in the WBP production industries to reduce the amount of formaldehyde emission from the WBPs.
Various methods have been used for reducing the amount of formaldehyde emission from WBPs. Examples include but are not limited to optimization of formaldehyde to urea molar ratio in the adhesive compositions, modification of urea formaldehyde resin with melamine, phenol, etc., application of alternative resins (e.g. natural resin and non-formaldehyde synthetic resins), replacement of formaldehyde by alternative aldehydes (e.g. isobutyraldehyde, succinaldehyde, glyoxal-aldehyde etc.), optimization of the WBP production process, panel preparation and post-production treatments, and application of formaldehyde scavengers. These methods are associated with problems, though, such as lower water resistance of the produced WBPs in case of using natural resins as adhesive or higher cost of alternative adhesive compositions.
Application of formaldehyde scavengers seems to be a promising method for reducing the amount of formaldehyde emission from WBPs. Urea and ammonium derivatives are the most typical formaldehyde scavengers that may be used in the adhesive compositions. However, application of urea and ammonium derivatives may affect the physical and mechanical properties of the WBPs. There is an ongoing need in the art for an eco-friendly, bio-based and biodegradable composition that may be used as a formaldehyde scavenger. Also, there is a need in the art for a formaldehyde scavenger capable of reducing the amount of formaldehyde emission from the WBPs while not significantly affecting the physical and mechanical properties of the WBPs, such as modulus of elasticity, bending strength, internal bonding, thickness swelling, and water absorption.